By 1987, Prince was three years beyond the star-making phenomenon of Purple Rain, but it seemed like much longer. He was still a huge star, but some overly ambitious—or overly self-indulgent—artistic decisions put his status on music’s A-list in jeopardy.

He’d followed the massive superstardom of the 1984 Purple Rain album, movie and blockbuster tour less than a year later with the decidedly different and dense Around the World in a Day, which was packed with psychedelic spirituality, and which featured just two hits, “Raspberry Beret” and “Pop Life.” At Prince’s insistence, the album was marketed as minimally as the massive Warner Brothers Records machine would allow.

With 1986 came the arrival of the striking, minimalist full-length Parade. While lauded critically and instantly embraced by the Prince faithful, like its predecessor, the album spawned just one U.S. hit: “Kiss” (although to be fair, it also has the classics “Sometimes It Snows in April” and “Mountains”).

1986 also saw Prince take a popular and critical drubbing with the release of the movie Under the Cherry Moon. While the movie’s soundtrack (the aforementioned Parade) was a success, the campy, black and white picture would earn a slew of negative “accolades,” include five awards at the following year’s Razzie Awards. The film “won” Worst Picture (tied with Howard the Duck!), while Prince got the dubious honor of Worst Actor and Worst Director. Adding insult to injury, he also got Worst Original Song for “Love or Money.”

The end of the Parade tour signaled the end of Prince’s longtime band, the Revolution, with a chaotic show in Japan that would be the last time the classic lineup would play together.

Freshly liberated from the Revolution, Prince went into 1987 with a chip on his shoulder. Eager to bounce back from Under the Cherry Moon, he had plenty to prove with his next move. At the same time, his evolution as an artist found him wanting to push and transcend even more boundaries musically.

Consolidating a wealth of material originally slated for a Revolution album, (working title: Dream Factory), along with a planned side project under the name of Camille (according to one account, he had a full album’s worth of songs for the project written on a single plane ride), Prince’s return would come in the form of an ambitious double-album, Sign o’ the Times.

The result of a begrudging compromise to pair down what he wanted to be a triple-album called Crystal Ball into a two-LP set, Sign o’ the Times hit record store shelves on the last day of March 1987 featuring entirely new sides to Prince’s artistic persona (it would also be the source of a fantastic concert movie of the same name, which remains criminally out of print).

Thanks, in part, to the different projects time periods that the songs came from, the sprawling double-album covers a lot of territory—not always cohesively—and stands in stark contrast to the tightly-wound concepts of his earlier albums.

Opening with the topical, stripped-down title track, the album veers wildly from extreme to another. The jaunty, upbeat “Play in the Sunshine” careens into the stark dancefloor stomp of “Housequake” (a style he’d revisit later on the album with “Hot Thing”) before turning down for the quirky intimacy of “The Ballad of Dorothy Parker,” built atop Prince’s deft LinnDrum programming, wobbly synth melody and rumbling bass line. And that’s just side one.

This stylistic restlessness pervades the entire album. “Starfish and Coffee” recalls Paul McCartney at his most whimsical and melodic. The song is based on a true story of a childhood classmate told by Susannah Melvoin (singer for Prince spin-off act, the Family, and twin sister to the Revolution’s guitarist, Wendy Melvoin), earning her a songwriting credit.

The album features a pair of classic Prince love ballads, “Slow Love” and “Adore,” both more refined takes on the torchy style he’d previously used on older tracks including “Do Me, Baby” and “International Lover.”

Among the album’s best tracks is “If I Was Your Girlfriend”—one of the songs originally intended for the Camille project—which uses the pitched-up vocal style to great effect while pondering life as his lover’s platonic female friend.

Some of the most memorable moments come when Prince takes on straight-up arena-rock. Featuring percussion from longtime protégé Sheila E. and a co-lead vocal from Scottish pop star, Sheena Easton, rock rave-up “U Got the Look” would soar to No. 2 on the Billboard Hot 100.

Prince goes even broader on the poppy jam, “I Could Never Take the Place of Your Man,” a revived song from 1982 that’s also marked by an extended, bluesy breakdown before launching back into song’s rousing chorus melody for another go-round.

The slow burn religious fervor of “The Cross” builds from a strummed guitar and Prince’s emotive vocals into a thunderous arena-rock anthem that at 4:45 ends far too soon, begging for a drawn-out, concert-style jam.

“‘The Cross’ was one of what I used to call ‘Sunday songs,’ remembered longtime studio engineer, Susan Rogers, in a 2013 interview. “Some of his deepest, most introspective and most important songs I noticed were recorded on Sundays.”

The luxury of length is afforded to “It’s Gonna Be a Beautiful Night,” a nine-minute funk workout mostly recorded live onstage with the Revolution in Paris over the summer of 1986 on the Parade tour. Sheila E. would literally phone-in her mid-song rap during a studio session months later.

Fascinating, gleefully weird at points, while surprisingly conventional (well, as conventional as Prince could possibly be) at others, Sign o’ the Times finds Prince exploring the outer reaches of his sound, from home studio auteur to stadium-filling guitar god.

Considered by many to be his creative magnum opus, Sign o’ the Times forever stands as a significant totem among Prince’s vast discography, when his boundless creativity still commanded cultural relevance while simultaneously rocking the upper echelon of the charts.